Looking through different reviews of this drama I was a little disappointed to see that it didn't get particularly good ratings, I love this drama and I would recommend it to anybody any day of the week.
The OST's were great (I'm listening to the sound track as I write this and it makes me want to rewatch the drama again), especially Memory by Ben, Because Of You by Kim EZ and One More Step by Sandeul- they're my favourites. The acting was well executed and the two leads played their characters well, it wasn't overdone or too melodramatic. There were sweet moments between the two leads, yes, you may have had to wait for them for a little while, but they happened eventually and they were incredible and worth waiting for.
I especially liked the acting of the second male lead, Yoon Park is a great actor who always portrays his roles well- In 'Hello My Twenties' he made me love his character so much, while in 'Introverted Boss' he made me hate him at moments and then love him at others. I really commend him for being to be able have that sort of duality.
I loved how you really got to watch Eun Hwan-Ki come out of his shell and get more comfortable with the Silent Monster team, many people argued that it happened too fast and it didn't really make much sense with the timing of events- but I disagree, I loved this aspect of the drama and loved seeing all the weird situations he got in when trying to help out his team-mates.
Another aspect of the drama that I loved is how sweet Eun Hwan-Ki (the male lead) is and how the drama portrayed this, everything he does he does it when thinking of how it will benefit others. He's just a shy little boy trying to express himself in the best way he can- yes it does come off as a bit creepy at the start of the drama but you learn to love his quirks and oddities as the drama progresses.

All in all I'd really recommend this drama, give a bit of time (don't drop it too soon) and I'm sure you'll come to love it as much as I do. Don't judge it too harshly at the start and go into watching it with an open mind. Everything will make sense at the end of the drama so don't get confused when it's a bit convoluted. Good luck :))